Inclusion Criteria

DISEASE CHARACTERISTICS:

- Histologically confirmed solid tumor (phase I, stratum A1 or A2) or neuroblastoma
(phase II, stratum B) or relapsed/refractory acute lymphoblastic leukemia (ALL)
(phase II, stratum C) (ALL closed to accrual as of 02/18/10)

- Relapsed or refractory

- Patients with leukemia who relapse during standard maintenance therapy are
eligible at time of relapse (closed to accrual as of 02/18/10)

- Meets the following criteria for measurable or evaluable disease as defined below by
stratum:

- Stratum A1 or A2: measurable or evaluable disease

- Stratum B: meets 1 of the following criteria:

- Measurable tumor on MRI, CT scan, or x-ray obtained within 4 weeks prior to
study entry

- Evaluable tumor by MIBG scan or bone marrow involvement with tumor cells
seen on routine morphology

- Stratum C: must have M3 bone marrow (closed to accrual as of 02/18/10)

- No existing curative therapy for the disease or therapy proven to prolong survival
with an acceptable quality of life

- No CNS tumors, known CNS metastatic disease, or known CNS leukemia

PATIENT CHARACTERISTICS:

- Karnofsky performance status (PS) 50-100% (patients > 16 years of age) OR Lansky PS
50-100% (patients ≤ 16 years of age)

- Patients with solid tumors (phase I, stratum A1 or A2) must meet the following
hematopoietic criteria:

- ANC ≥ 1,000/μL

- Platelet count ≥ 100,000/μL (no platelet transfusions within 7 days prior to
enrollment)

- Hemoglobin ≥ 8.0 g/dL (transfusion allowed)

- Patients in phase II portion of the study (stratum B & C) must meet the following
hematopoietic criteria: (stratum C closed to accrual as of 02/18/10)

- ANC ≥ 750/μL

- Platelet count ≥ 50,000/μL (transfusion allowed)*

- Hemoglobin ≥ 8.0 g/dL (transfusion allowed)* NOTE: * Patients with leukemia must
not be refractory to red blood cell or platelet transfusions (closed to accrual
as of 02/18/10)

- Creatinine clearance or radioisotope glomerular filtration rate ≥ 70ml/min OR serum
creatinine based on age/gender (male [M], female [F]) as follows (in mg/dL):

- 0.6(M), 0.6(F) (for patients 1 to < 2 years of age)

- 0.8(M), 0.8(F) (for patients 2 to < 6 years of age)

- 1(M), 1(F) (for patients 6 to < 10 years of age)

- 1.2(M), 1.2(F) (for patients 10 to < 13 years of age)

- 1.5(M), 1.4(F) for patients 13 to < 16 years of age)

- 1.7(M), 1.4(F) (for patients 16 years of age and over)

- Bilirubin ≤ 1.5 times upper limit of normal (ULN) for age

- ALT ≤ 5.0 times ULN for age

- Serum albumin ≥ 2 g/dL

- Not pregnant or nursing

- Negative pregnancy test

- Fertile patients must use effective contraception

- No uncontrolled infection

- Patients must be able to swallow capsules

- No patients who are unable to comply with the safety monitoring requirements of the
study, in the opinion of the investigator

PRIOR CONCURRENT THERAPY:

- Recovered from prior chemotherapy, immunotherapy, or radiotherapy

- More than 3 weeks since prior myelosuppressive chemotherapy (6 weeks for nitrosourea)
(stratum A1 or A2)

- At least 14 days since prior cytotoxic therapy

- At least 24 hours since cytoreduction with hydroxyurea

- At least 7 days since prior hematopoietic growth factor therapy

- At least 7 days since prior biological therapy (anti-neoplastic agent)

- At least 2 weeks since prior local palliative external radiotherapy (XRT) (small
port)

- At least 6 weeks since prior treatment with therapeutic doses of iodine I 131
metaiodobenzylguanidine

- At least 6 months since prior total-body irradiation (TBI), craniospinal XRT, or
radiation to more than 50% of pelvis

- At least 6 weeks since prior other substantial bone marrow radiation

- At least 3 months since prior stem cell transplant or rescue without TBI AND no
evidence of active graft vs host disease

- At least 3 half-lives since prior therapy that includes a monoclonal antibody

- More than 7 days since prior growth factors that support platelet or white cell
number or function

- Concurrent corticosteroids allowed provided patient is on a stable or decreasing dose
of corticosteroid for ≥ 7 days prior to study enrollment

- No other concurrent investigational drug

- No other concurrent anticancer therapy, including chemotherapy, radiotherapy,
immunotherapy, or biological therapy

- Concurrent intrathecal methotrexate allowed for patients with ALL at the
discretion of the treating investigator

- No concurrent P-gp substrates (i.e., digoxin, cyclosporine, tacrolimus, or sirolimus)

- No concurrent chronic benzodiazepines